U.S. patent number 7,096,608 [Application Number 10/655,840] was granted by the patent office on 2006-08-29 for overload prevention device for a snow removing machine.
This patent grant is currently assigned to Honda Giken Kogyo Kabushiki Kaisha. Invention is credited to Yasutomo Abe, Kenji Kamata, Kenji Kuroiwa, Tsutomu Mizoroke.
United States Patent |
7,096,608 |
Kuroiwa , et al. |
August 29, 2006 |
Overload prevention device for a snow removing machine
Abstract
An overload prevention device has a first rotational member for
driving engagement with an input shaft of an auger transmission of
a snow removing machine, a second rotational member engaging the
first rotational member for rotation therewith over a predetermined
torque range and for rotation relative thereto when a predetermined
torque is exceeded, and a movable member mounted adjacent to the
first rotational member for undergoing movement to restrict a
rotating angle of the second rotational member. A detector outputs
a detection signal each time the detector detects movement of the
movable member in a direction away from the first rotational member
when protuberances of the movable member engage protrusions of the
first rotational member responsive to relative rotation between the
first and second rotational members. A control unit stops operation
of the engine when the detector outputs the detection signal a
preselected number of times within a preselected time period.
Inventors: |
Kuroiwa; Kenji (Wako,
JP), Kamata; Kenji (Wako, JP), Abe;
Yasutomo (Wako, JP), Mizoroke; Tsutomu (Wako,
JP) |
Assignee: |
Honda Giken Kogyo Kabushiki
Kaisha (Tokyo, JP)
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Family
ID: |
31996179 |
Appl.
No.: |
10/655,840 |
Filed: |
September 5, 2003 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20040049953 A1 |
Mar 18, 2004 |
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Foreign Application Priority Data
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Sep 13, 2002 [JP] |
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2002-268753 |
Mar 13, 2003 [JP] |
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2003-067596 |
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Current U.S.
Class: |
37/245; 37/244;
477/178 |
Current CPC
Class: |
E01H
5/04 (20130101); Y10T 477/759 (20150115) |
Current International
Class: |
E01H
5/09 (20060101) |
Field of
Search: |
;37/244,245,249,253
;477/178,177 ;192/56.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1 186 716 |
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Mar 2002 |
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EP |
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51034111 |
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Aug 1976 |
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JP |
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Primary Examiner: Beach; Thomas A
Attorney, Agent or Firm: Adams & Wilks
Claims
What is claimed is:
1. An overload prevention device for an auger transmission of a
snow removing machine for preventing an excessive load from acting
on a power train of the auger transmission from an engine to an
auger and an auger shaft of the snow removing machine, the overload
prevention device comprising: a worm wheel meshing with a worm
formed on an input shaft of the auger transmission, the worm wheel
having a plurality of wheel protrusions formed at a side surface
thereof; a cylindrical member integrally connected to the auger
shaft and engaging with the worm wheel for rotation therewith over
a predetermined torque range and for rotation relative thereto when
a predetermined torque is exceeded; a generally disk-shaped member
disposed adjacent to the worm wheel for restricting a rotating
angle of the cylindrical member, the disk-shaped member having a
plurality of generally disk-shaped protuberances facing the wheel
protrusions of the worm wheel; a detector for outputting a
detection signal each time the detector detects movement of the
disk-shaped member away from the side surface of the worm wheel
when the protuberances of the disk-shaped member ride on the wheel
protrusions of the worm wheel responsive to rotation of the
cylindrical member and the worm wheel relative to one another, the
detector having an ON state corresponding to a state during which
the detector outputs the detection signal and an OFF state
corresponding to a state during which the detector does not output
the detection signal; a control unit for stopping operation of the
engine when the detector outputs the detection signal a preselected
number of times within a preselected time period; and a stopper
member for temporarily stopping movement of the disk-shaped member
to restore the detector to the OFF state from the ON state.
2. An overload prevention device for an auger transmission of a
snow removing machine for preventing an excessive load from acting
on a power train of the auger transmission from an engine to an
auger and an auger shaft of the snow removing machine, the overload
prevention device comprising: a worm wheel meshing with a worm
formed on an input shaft of the auger transmission, the worm wheel
having a plurality of wheel protrusions formed at a side surface
thereof, each of the wheel protrusions having a top portion having
a planar surface extending in a direction generally perpendicular
to an axis of rotation of the worm wheel; a cylindrical member
integrally connected to the auger shaft and engaging with the worm
wheel for rotation therewith over a predetermined torque range and
for rotation relative thereto when a predetermined torque is
exceeded; a generally disk-shaped member disposed adjacent to the
worm wheel for restricting a rotating angle of the cylindrical
member, the disk-shaped member having a plurality of generally
disk-shaped protuberances facing the wheel protrusions of the worm
wheel; a detector for outputting a detection signal each time the
detector detects movement of the disk-shaped member away from the
side surface of the worm wheel when the protuberances of the
disk-shaped member ride on the wheel protrusions of the worm wheel
responsive to rotation of the cylindrical member and the worm wheel
relative to one another; and a control unit for stopping operation
of the engine when the detector outputs the detection signal a
preselected number of times within a preselected time period.
3. An overload prevention device according to claim 2; wherein each
of the protuberances of the disk-shaped member comprises a first
louver-shaped portion and a second louver-shaped portion; and
wherein a distance between confronting tip portions of the first
and second louver-shaped portions is shorter than a length of the
planar surface of the top portion of the wheel protrusion.
4. A combination according to claim 1; further comprising a biasing
member for biasing the stopper member in the direction of the
movable member.
5. A combination according to claim 1; wherein the stopper member
is mounted for undergoing sliding movement in a direction generally
perpendicular to the surface of the first rotational member at
which the protrusions are formed.
6. A combination according to claim 1; wherein the stopper member
is slidably received in a transmission case of the auger
transmission.
7. An overload prevention device according to claim 1; further
comprising a biasing member for biasing the stopper member in the
direction of the disk-shaped member.
8. An overload prevention device according to claim 1; wherein the
stopper member is mounted for undergoing sliding movement in a
direction generally perpendicular to the side surface of the worm
wheel.
9. An overload prevention device according to claim 1; wherein the
stopper member is slidably received in a transmission case of the
auger transmission.
10. An overload prevention device for an auger transmission of a
snow removing machine for preventing an excessive load from acting
on a power train of the auger transmission from an engine to an
auger and an auger shaft of the snow removing machine, the overload
prevention device comprising: a worm wheel meshing with a worm
formed on an input shaft of the auger transmission, the worm wheel
having a plurality of wheel protrusions formed at a side surface
thereof; a cylindrical member integrally connected to the auger
shaft and engaging with the worm wheel for rotation therewith over
a predetermined torque range and for rotation relative thereto when
a predetermined torque is exceeded; a generally disk-shaped member
disposed adjacent to the worm wheel for restricting a rotating
angle of the cylindrical member, the disk-shaped member having a
plurality of generally disk-shaped protuberances facing the wheel
protrusions of the worm wheel; a detector for outputting a
detection signal each time the detector detects movement of the
disk-shaped member away from the side surface of the worm wheel
when the protuberances of the disk-shaped member ride on the wheel
protrusions of the worm wheel responsive to rotation of the
cylindrical member and the worm wheel relative to one another; and
a control unit for stopping operation of the engine when the
detector outputs the detection signal a preselected number of times
within a preselected time period; wherein the control unit
comprises a signal processing circuit for receiving and processing
the detection signal from the detector, a control integrated
circuit for controlling operation of the engine in accordance with
a signal from the signal processing circuit, a reset timer
initiated by a command signal from the control integrated circuit
when the signal processing circuit receives the detection signal
from the detector, and an engine stopping circuit for stopping
operation of the engine in accordance with a control signal from
the control integrated circuit when the detection signal of the
detector is outputted a preselected number of times within the
preselected time period.
11. In combination with a snow removing machine having an engine,
an auger, and an auger transmission for transmitting power from the
engine to the auger, an overload prevention device for preventing
an excessive load on the auger transmission, the overload
prevention device comprising: a first rotational member connected
to be rotationally driven by an input shaft of the auger
transmission, the first rotational member having a plurality of
protrusions formed at a surface thereof; a second rotational member
engaging the first rotational member for rotation therewith over a
predetermined torque range and for rotation relative thereto when a
predetermined torque is exceeded; a movable member mounted adjacent
to the first rotational member for undergoing movement to restrict
a rotating angle of the second rotational member, the movable
member having a plurality of protuberances for engagement with the
protrusions of the first rotational member; a detector for
outputting a detection signal each time the detector detects
movement of the movable member in a direction away from the first
rotational member when the protuberances of the movable member
engage the protrusions of the first rotational member responsive to
rotation of the second rotational member and the first rotational
member relative to one another, the detector having an ON state
corresponding to a state during which the detector outputs the
detection signal and an OFF state corresponding to a state during
which the detector does not output the detection signal; a control
unit for stopping operation of the engine when the detector outputs
the detection signal a preselected number of times within a
preselected time period; and a stopper member for temporarily
stopping movement of the third rotational member to restore the
detector to the OFF state from the ON state.
12. In combination with a snow removing machine having an engine,
an auger, and an auger transmission for transmitting power from the
engine to the auger, an overload prevention device for preventing
an excessive load on the auger transmission, the overload
prevention device comprising: a first rotational member connected
to be rotationally driven by an input shaft of the auger
transmission, the first rotational member having a plurality of
protrusions formed at a surface thereof, each of the protrusions
having a portion having a planar surface extending in a direction
generally perpendicular to an axis of rotation of the first
rotational member; a second rotational member engaging the first
rotational member for rotation therewith over a predetermined
torque range and for rotation relative thereto when a predetermined
torque is exceeded; a movable member mounted adjacent to the first
rotational member for undergoing movement to restrict a rotating
angle of the second rotational member, the movable member having a
plurality of protuberances for engagement with the protrusions of
the first rotational member; a detector for outputting a detection
signal each time the detector detects movement of the movable
member in a direction away from the first rotational member when
the protuberances of the movable member engage the protrusions of
the first rotational member responsive to rotation of the second
rotational member and the first rotational member relative to one
another; and a control unit for stopping operation of the engine
when the detector outputs the detection signal a preselected number
of times within a preselected time period.
13. A combination according to claim 12; wherein each of the
protuberances of the movable member comprises a first louver-shaped
portion and a second louver-shaped portion; and wherein a distance
between confronting tip portions of the first and second
louver-shaped portions is shorter than a length of the planar
surface of the top portion of the first rotational member.
14. In combination with a snow removing machine having an engine,
an auger, and an auger transmission for transmitting power from the
engine to the auger, an overload prevention device for preventing
an excessive load on the auger transmission, the overload
prevention device comprising: a first rotational member connected
to be rotationally driven by an input shaft of the auger
transmission, the first rotational member having a plurality of
protrusions formed at a surface thereof; a second rotational member
engaging the first rotational member for rotation therewith over a
predetermined torque range and for rotation relative thereto when a
predetermined torque is exceeded; a movable member mounted adjacent
to the first rotational member for undergoing movement to restrict
a rotating angle of the second rotational member, the movable
member having a plurality of protuberances for engagement with the
protrusions of the first rotational member; a detector for
outputting a detection signal each time the detector detects
movement of the movable member in a direction away from the first
rotational member when the protuberances of the movable member
engage the protrusions of the first rotational member responsive to
rotation of the second rotational member and the first rotational
member relative to one another; and a control unit for stopping
operation of the engine when the detector outputs the detection
signal a preselected number of times within a preselected time
period; wherein the control unit comprises a signal processing
circuit for receiving and processing the detection signal from the
detector, a control integrated circuit for controlling operation of
the engine in accordance with a signal from the signal processing
circuit, a reset timer initiated by a command signal from the
control integrated circuit when the signal processing circuit
receives the detection signal from the detector, and an engine
stopping circuit for stopping operation of the engine in accordance
with a control signal from the control integrated circuit when the
detection signal of the detector is outputted a preselected number
of times within the preselected time period.
Description
FIELD OF THE INVENTION
The present invention relates to an overload prevention device for
a snow-removing machine for preventing an excessive load acting on
a power train from an engine to an auger of the snow-removing
machine.
BACKGROUND OF THE INVENTION
Snow-removers which clear snow by transmitting power from an engine
to an auger and rotating the auger have been known (e.g.,
JP-UM-B-51-34111).
Such a snow-remover is comprised of a drive pulley attached to an
output shaft of an engine, a belt trained around the drive pulley
and a driven pulley, a rotating transmission shaft extending
forward from the driven pulley, a rotating auger shaft connected to
the front end of the rotating transmission shaft by way of a gear
case, and an auger attached to the rotating auger shaft.
For example, during snow-removing work, it sometimes happens that
the auger bites into a lump of ice or a stone or the like and the
rotation of the auger is stopped, causing an excessive load to act
on the power train from the engine to the auger. It is desirable
for this kind of excessive load to be eliminated.
However, when an overload is detected, for example if the engine is
stopped by instantaneous overloads occurring at times such as when
the auger hits a curbstone or the like, or if the engine is stopped
by noise from a detector for detecting overloads, optimal overload
prevention cannot be achieved. That is, it is desirable for
instantaneous overloading occurring when the auger hits a curbstone
or the like and erroneous overloading caused by detector noise to
be distinguished from continuous overloading caused by the auger
biting into snow or debris. That is, in a snow-remover, an overload
prevention device which can surely determine that overloading has
occurred, and deal with this overloading, is desirable.
SUMMARY OF THE INVENTION
According to the present invention, there is provided an overload
prevention device for a snow-remover for, in the transmission of
power from an engine through an auger transmission to an auger
shaft and an auger in turn, preventing an excessive load from
acting on the power train from the engine to the auger, the
overload prevention device comprising: a worm wheel for meshing
with a worm provided on an input shaft of the auger transmission; a
cylindrical member which is fitted in the worm wheel and
consequently rotates integrally therewith over a predetermined
torque range and rotates relative thereto when a predetermined
torque is exceeded, and which is attached integrally to the auger
shaft; a disk-shaped member which is limited in angle of turn with
respect to the cylindrical member and is adjacent to the worm wheel
and has plurality of disc protuberances facing a plurality of wheel
protrusions provided on a side face of the worm wheel; a detector
which detects movement of the disc away from the side face of the
worm wheel when due to turning of the cylindrical member relative
to the worm wheel the disc protuberances mount the wheel
protrusions; and a control unit which stops the engine when the
number of times a detection signal is generated by the detector
reaches a predetermined number of times within a predetermined
period.
By a control unit being provided which stops the engine when the
number of times a detection signal is generated by the detector
reaches a predetermined number of times, instantaneous overloading
occurring when the auger hits a curbstone or the like is
distinguished from continuous overloading caused by the auger
biting into snow or debris. As a result, unnecessary stopping of
the engine can be avoided, and the efficiency of snow-removing work
can be improved.
Preferably, each of the wheel protrusions has a flat part at its
top. In this case, when the disc has mounted the wheel side part,
the detector detects for a predetermined time that the disc has
moved in the direction of the side face of the worm wheel. As a
result, detector noise can be prevented from being erroneously
recognized as overload, and stable control of the overload
prevention device can be carried out.
BRIEF DESCRIPTION OF THE DRAWINGS
A preferred embodiment of the invention will now be described in
detail, by way of example only, with reference to the accompanying
drawings, in which:
FIG. 1 is a side view of a snow-remover equipped with an overload
prevention device according to the invention;
FIG. 2 is an exploded perspective view of an auger transmission
incorporating an overload prevention device according to the
invention;
FIG. 3 is a perspective view of a worm wheel shown in FIG. 2;
FIG. 4 is a sectional view taken along line 4--4 in FIG. 3;
FIG. 5 is a perspective view of a slide washer shown in FIG. 2;
FIG. 6 is a sectional view taken along line 6--6 in FIG. 5;
FIG. 7 is a sectional view showing a relationship between a slide
washer and a stopping member;
FIG. 8 is a partial section view showing the relationship between
an auger transmission and an auger housing and a bracket;
FIG. 9 is a sectional front view of an auger transmission equipped
with an overload prevention device according to the invention;
FIG. 10 is a sectional side view of an auger transmission equipped
with an overload prevention device according to the invention;
FIG. 11 is an electrical block diagram of a control unit of an
overload prevention device according to the invention;
FIG. 12 is a timing chart of a signal outputted from a washer
detector switch;
FIG. 13 is a flow chart of the control unit shown in FIG. 11;
FIG. 14 is a view showing the rotation of an auger being obstructed
during travel of a snow-remover; and
FIG. 15 through FIG. 22 are views showing operating states of a
worm wheel, a boss member and a slide washer.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
A snow-remover 10 shown in FIG. 1 has a machine frame 11, left and
right crawlers 12 (the right crawler is not shown), a handle 13, an
engine 15, a drive shaft 16, an auger 23, and a shooter 24.
The handle 13 extends rearward and upward from the machine frame 11
and has at its end a grip 14.
The engine 15 is mounted on the top of the machine frame 11. A
drive shaft 16 rotated by this engine 15 extends in front of the
machine frame 11 and is connected to an auger transmission 18
incorporating an overload prevention device 60 (see FIG. 9 and FIG.
10). A blower 21 is attached to the drive shaft 16. The auger 23 is
attached to an auger shaft 22 of the auger transmission 18. The
reference number 25 denotes an auger housing.
The drive shaft 16 and the auger transmission 18 constitute a
"power transmission device" for transmitting power from the engine
15 to the auger 23.
In this snow-remover 10, the operation of the engine 15 rotates the
drive shaft 16, the blower 21 is rotated by the drive shaft 16, and
the auger 23 is rotated by way of the auger transmission 18. Snow
shifted by the auger 23 is scooped up and blown far away through
the shooter 24 by the blower 21.
Next, the auger transmission 18 of the power transmission device
will be described, on the basis of FIG. 2.
The auger transmission 18 consists of a worm speed-reducer. This
auger transmission 18 has a transmission case 33, an input shaft
36, a worm wheel 38 (first rotational member) an auger shaft 22, a
washer detector switch 53, and a stopping member 59.
The transmission case 33 is made up of a case proper 31 and a case
cover 32.
The input shaft 36 is mounted to the transmission case 33 on
bearings 34, 35 and connected to the drive shaft 16 shown in FIG.
1. A worm 37 is formed on the input shaft 36.
The worm wheel 38 meshes with the worm 37. A cylindrical member
(second rotational member) consisting of a cylindrical boss member
41 fits in the center of this worm wheel 38. A female spline 42 is
formed in this boss member 41.
The auger shaft 22 has a male spline 43 which mates with the female
spline 42. The auger shaft 22 is supported on bearings 51, 52
mounted to the case proper 31.
A slide washer 45 is is in the form of a generally disk-shaped
member (movable member) adjacent to the worm wheel 38. This slide
washer 45 is pressed against the worm wheel 38 by an elastic member
46. The elastic member 46 is pressed by a support plate 47
positioned on its outer side.
The washer detector switch 53 is a detector for detecting movement
of the slide washer 45 away from one side face of the worm wheel
38.
The stopping member 59 temporarily stops movement of the slide
washer 45, to restore the washer detector switch 53 to an initial
state (an OFF state).
A receiving part 54 for receiving the stopping member 59 is formed
on the case proper 31. A mounting part 55 for mounting the washer
detector switch 53 to is formed on the case proper 31. An oil hole
for pouring oil into the transmission case 33 through is plugged by
a plugging bolt 56 fitted with a washer. Multiple bolts 57 (of
which only one is shown in FIG. 2) hold together the case proper 31
and the case cover 32 with a gasket 62 therebetween.
In the figures, the reference number 63 denotes a circlip, and 64
through 66 are oil seals. The reference number 67 denotes a case
cap. The stopping member 59 is urged into the receiving part 54 of
the case proper 31 at all times by means of a biasing member, such
as a compression spring 68, and a stopping member retainer 69. The
washer detector switch 53 is protected by a protective switch cover
72. The reference number 73 denotes a bracket, and 74 is a switch
side bracket. The reference numbers 75, 76 denote bolts, and 77, 78
are nuts.
The overload prevention device 60 shown in FIG. 9 and FIG. 10, as
will be further discussed later, has as its main parts the worm
wheel 38, the boss member 41, the slide washer 45, the elastic
member 46, the support plate 47, the washer detector switch 53, the
stopping member 59 and a control unit 105 (see FIG. 9 and FIG.
10).
The worm wheel 38 is shown in detail in FIG. 3 and FIG. 4.
The worm wheel 38 has multiple teeth 81 for messing with the worm
37 (see FIG. 2), a fitting hole 82 into which the boss member 41
fits, and a plurality of wheel protrusions 83 to which the slide
washer 45 (see FIG. 2) is fitted. Each of the wheel protrusions 83
has a flat part 87 at its top. Stated otherwise, a top portion of
each of the wheel protrusions 83 has a planar surface extending in
a direction generally perpendicular to an axis of rotation of the
worm wheel 38.
The circumferential part 84 of the boss member 41 fits in the
fitting hole 82 of the worm wheel 38. By the male spline 43 of the
auger shaft 22 (see FIG. 2) and the female spline 42 formed on the
boss member 41 mating, the auger shaft 22 and the worm wheel 38 are
connected. The boss member 41 has a plurality of external
projections 85 with which the slide washer 45 shown in FIG. 2
engages.
The boss member 41 is retained in the worm wheel 38 by a retaining
ring 86. The reference letter A denotes the width of the flat parts
87.
Next, the construction of the slide washer 45 will be described,
with reference to FIG. 5 and FIG. 6.
The disk-shaped slide washer 45 has a fitting hole 91 into which
the boss member 41 shown in FIG. 3 fits; a plurality of internal
projections 92 for engaging with the plurality of external
projections 85 formed on the outside of the boss member 41;
generally disk-shaped protuberances 93 (hereinafter "disc
protuberances") for engaging with the wheel protrusions 83,
protruding toward the side face of the worm wheel 38 (see FIG. 3);
a plurality of stopping parts 96 which to stopping member 59 shown
in FIG. 2 stops; and a plurality of escape holes 97 which avoid the
engagement of the stopping member 59. The disc protuberances 93 are
formed by cutting lines in a disc and a carrying out a louvering
process in which those parts are raised.
As shown in FIG. 6, each of the disc protuberances 93 is made up of
a first louver part 94 and a second louver part 95. The distance B1
from the tip of the first louver part 94 to the tip of the second
louver part 95 is shorter than the length A of the flat part 87
shown in FIG. 4. Consequently, the disc protuberances 93 can easily
pass over the flat part 87 without fitting onto the wheel
protrusions 83.
The width B of the disc protuberances 93, which ride over the flat
parts 87 of the wheel protrusions 83, is determined in
consideration of the speed of rotation of the worm wheel 38
As shown in FIG. 7, the stopping member 59 is slidably received in
the receiving part 54 of the case proper 31. This stopping member
59 is urged in the direction of the slide washer 45 by the
compression spring 68. This compression spring 68 is supported by
the stopping member retainer 69. The stopping member 59 slides
perpendicularly with respect to the side face of the worm wheel 38
along with movement of the slide washer 45.
That is, when the slide washer 45 moves as shown by arrow [1] from
the position shown with solid lines to the position shown with
broken lines, the stopping member 59 withdraws as shown by arrow
[2]. The stopping member 59 restores the washer detector switch 53
shown in FIG. 2 to an initial state.
As will be further discussed later, when it is positioned in an
escape hole 97 of the slide washer 45 (see FIG. 5), the stopping
member 59 is kept in a projecting state by the compression spring
68. When the slide washer 45 rotates and the stopping member 59
hits a stopping part 96, the rotation of the slide washer 45 stops.
When it is positioned on any other part of the slide washer 45, the
stopping member 59 withdraws against the resistance of the
compression spring 68.
FIG. 8 shows the relationship between the auger transmission 18,
the auger housing 25 and the bracket 73.
A case mounting part 101 of the bracket 73 is attached to the case
proper 31 of the auger transmission 18 with the bolts 75 and the
nuts 77. A housing mounting part 102 of this bracket 73 is attached
to the inside of the auger housing 25 with bolts 107, 107. The
protective switch cover 72 is fitted over the washer detector
switch 53, and the washer detector switch 53 is connected to the
control unit 105 by a lead wire 103. This lead wire 103 passes
through the inside of a pipe part 104 of the bracket 73. The switch
bracket 74, which covers the washer detector switch 53 and the
stopping member 59, is attached to the bracket 73 with a bolt 76
and a nut 78.
FIG. 9 and FIG. 10 show the auger transmission 18 with its overload
prevention device 60 in sectional view.
The worm wheel 38, as a result of the boss member 41 being
press-fitted in its fitting hole 82, rotates integrally with the
boss member 41 as long as it is transmitting a normal torque.
However, when a torque above a predetermined level (an excessive
torque) acts on the auger shaft 22, the worm wheel 38 rotates
freely relative to the boss member 41, or the boss member 41
rotates freely relative to the worm wheel 38.
Preferably, a sulfurizing treatment is carried out on the face of
the worm wheel 38 forming the fitting hole 82 and the
circumferential face 84 of the boss member 41, of the overload
prevention device 60. This sulfurizing treatment is a metal surface
treatment which diffuses free sulfur into a surface layer of a
ferrous material (carbon steel, cast iron, cast steel, stainless
steel etc.). Because free sulfur is a rich lubricant, when rubbing
of opposing contacting faces occurs due to slipping, wear is
suppressed and resistance to wear increases.
Instead of sulfurizing treatment, carburizing treatment, or a
combination of sulfurizing and carburizing, may alternatively be
carried out on the fitting hole 82 of the worm wheel 38 and the
circumferential face 84 of the boss member 41.
The washer detector switch 53 consists of a limit switch attached
to the case proper 31. This switch 53 has a depressable contact 108
for detecting that the slide washer 45 has moved perpendicularly
with respect to the side face of the worm wheel 38. With the state
of this contact 108 being advanced (the state in which the slide
washer 45 is shown with solid lines) as an OFF state and the state
of this contact 108 being withdrawn (the state in which the slide
washer 45 is shown with broken lines) as an ON state, it transmits
ON/OFF information to the control unit 105.
The protective switch cover 72 covers the washer detector switch 53
and thereby protects the washer detector switch 53 from snow and
water and so on. That is, by waterproofing the washer detector
switch 53, which is a detecting part of a signal system, the life
of the washer detector switch 53 is extended, and highly reliable
control of the overload prevention device 60 is realized.
The switch bracket 74 covers en bloc the washer detector switch 53,
the protective switch cover 72 and the lead wire 103 (see FIG. 8),
and thereby protects these detecting parts of the signal system
from being hit by small stones and the like.
Even if the attachment of the protective switch cover 72 to the
washer detector switch 53 is imperfect, as a result of the switch
bracket 74 being attached to the case proper 31 by way of the
bracket 73 (see FIG. 8), it presses the protective switch cover 72
and fufils the attachment of this protective switch cover 72 so
that the protective switch cover 72 is surely attached to the
washer detector switch 53.
The overload prevention device 60 prevents an excessive load from
acting on the power train from the engine 15 to the auger shaft 22
as power from the engine 15 is transmitted through the auger
transmission 18 to the auger shaft 22 and the auger 23 in turn.
The overload prevention device 60 has: the worm wheel 38, which
meshes with the worm 37 formed on the input shaft 36 (see FIG. 2)
of the auger transmission 18; the boss member (cylindrical member)
41, which as a result of being fitted in the worm wheel 38 rotates
integrally with it over a predetermined torque range but rotates
relatively to it when a predetermined torque is exceeded, and which
is integrally attached to the auger shaft 22; the slide washer 45,
which is limited in angle of turn with respect to the boss member
41 and is adjacent to the worm wheel 38 and has disc protuberances
93 facing the wheel protrusions 83 (see FIG. 3) provided on the
side face of the worm wheel 38; the washer detector switch 53,
which detects movement of the slide washer 45 away from the side
face of the worm wheel 38 when due to turning of the boss member 41
with respect to the worm wheel 38 the disc protuberances 93 mount
the wheel protrusions 83; and the control unit 105, which stops the
engine 15 when the number of times this detection is made by the
washer detector switch 53 reaches a predetermined number of times
within a predetermined period.
When a torque exceeding a predetermined value arises in the auger
shaft 22, relative rotation occurs between the worm wheel 38 and
the boss member 41, and the disc protuberances 93 of the slide
washer 45 mount the wheel protrusions 83 of the worm wheel 38, and
as a result the slide washer 45 moves away from the side face of
the worm wheel 38, this movement of the slide washer 45 is detected
by the washer detector switch 53, and on the basis of information
from this washer detector switch 53 the engine 15 is forcibly
stopped.
At this time, instantaneous overloads occurring when the auger 23
(see FIG. 1) hits a curbstone or the like and erroneous overloads
caused by noise of the washer detector switch 53 and so on can be
distinguished from continuous overloading caused by biting into
snow or debris in the control of stopping of the engine 15.
That is, by a control unit 105 being provided which stops the
engine 15 (see FIG. 1) when the number of times the washer detector
switch 53 has made a detection reaches a predetermined number of
times within a predetermined period, instantaneous overloads
occurring when the auger 23 hits a curbstone or the like are
distinguished from continuous overloading caused by biting into
snow and debris. Therefore, unnecessary stopping of the engine 15
can be avoided and the efficiency of snow-removing work can be
improved.
FIG. 11 is an electrical block diagram of a control unit 105 of an
overload prevention device according to the invention.
The control unit 105 is made up of a signal-processing circuit 111,
which receives information from the washer detector switch 53; a
control IC (Integrated Circuit) 112 for controlling the engine 15
(see FIG. 1) on the basis of information from this
signal-processing circuit 111; a reset timer 113, started by a
command signal outputted from the control IC 112 when information
is received from the washer detector switch 53; an LED (Light
Emitting Diode) 114, which lights when information is received from
the washer detector switch 53; an LED driving circuit 115, for
lighting this LED 114; and an engine stopping circuit 116, for
stopping the engine 15 on an order from the control IC 112.
As shown in FIGS. 12A through 12C, the signal-processing circuit
111 performs processing to infer that a signal is being outputted
from the washer detector switch 53 (hereinafter abbreviated to that
the washer detector switch is ON) when the ON state of the washer
detector switch 53 has persisted for more than a predetermined
period T1, and to infer that it is just noise when the ON state has
persisted for less than the predetermined period T1. That is, when
as shown in FIG. 12A the ON state has persisted for less than the
predetermined period T1, the overload prevention device is not
operated.
To maintain the ON state for more than the predetermined period T1,
the width B of the disc protuberances 93 which mount the flat parts
87 of length A provided on the wheel protrusions 83 are set in
consideration of the speed of rotation of the worm wheel 38 shown
in FIG. 3.
When ON information has been outputted from the signal-processing
circuit 111 for longer than the predetermined period T1, the reset
timer 113 is started by the control IC 112. And, when as shown in
FIG. 12B there is only one ON information longer than the
predetermined period T1 in a predetermined period T2 from the timer
being started, it is inferred that it was a brief overload of the
kind which arises when the auger hits a curbstone or the like, or a
brief overload caused by detector noise, and it is not necessary to
stop the engine 15, and the overload prevention device 60 does not
operate.
When as shown in FIG. 12C there has been ON information a
predetermined number of times within the predetermined period T2,
the control IC 112 sends a command signal for stopping the engine
15 to the engine stopping circuit 116. That is, when there is ON
information longer than the time T1 a number of times within the
predetermined time T2, it is inferred that the auger 23 has bitten
into snow or the like and continuous slipping is occurring, and the
engine 15 is stopped.
By this means it is possible for it to be correctly determined that
the auger 23 (see FIG. 1) has bitten into snow or debris. For
example, the engine 15 (see FIG. 1) is not stopped on the basis of
instantaneous slipping occurring at times such as when the auger 23
hits a curbstone or the like. The engine 15 being stopped on the
basis of noise sent from the washer detector switch 53 (see FIG. 2)
caused by vibration can be avoided.
In this preferred embodiment, as shown in FIGS. 12A through 12C,
the reset timer 113 (see FIG. 11) is started the first time an ON
state of the washer detector switch 53 persists for longer than a
predetermined period T1, and then the engine 15 (see FIG. 1) is
stopped when a predetermined number of times is counted in a
predetermined period T2. That is, the ON state time and the number
of counts can be set freely.
The LED driving circuit 115 shown in FIG. 11 lights the LED, on a
command of the control IC 112, when a first ON information arrives
from the signal-processing circuit 111, and puts out the LED, on a
command signal from the control IC 112, when the engine 15 has
stopped.
Next, the operation of the control unit 105 shown in FIG. 11 will
be described, on the basis of the flow chart shown in FIG. 13.
ST01: It is monitored whether or not there has been a predetermined
ON signal (an ON state longer than the period T1) from the washer
detector switch 53. If YES, processing proceeds to ST02.
ST02: The reset timer 113 is started.
ST03: It is determined whether or not the predetermined period T2
has elapsed. If YES, it is inferred to have been a momentary slip,
and processing returns to ST01. If NO, processing proceeds to
ST04.
ST04: It is determined whether or not the predetermined ON signal
(the ON state longer than the period T1) has arisen a predetermined
number of times within the predetermined period T2. That is, by
ST03 and ST04 it is monitored whether or not there has been an ON
signal longer than the period T1 multiple times within the
predetermined period T2. When there has been this ON signal
multiple times, it is inferred to be continuous slipping, and when
there has been the ON signal only once, it is inferred to be an
incidence of momentary slipping.
ST06: The engine 15 is stopped.
ST07: The reset timer 113 is stopped.
As shown in FIG. 14, for example during snow-removal work with the
snow-remover 10 traveling as shown by the arrow a, when the auger
23 of the snow-remover 10 during snow-removal bites into a lump of
ice or a stone or hits a projecting part 123 of the road surface
122 as shown in this figure, the rotation of the rotating auger 23
shown by the arrow b is obstructed, and the load acting on the
auger 23 itself and on the power train from the engine 15 to the
auger 23 becomes excessive. In the figure, 121 is snow.
Next, the specific operation of the overload prevention device 60
when as described with reference to FIG. 14 the load acting on the
auger 23 itself and on the power train from the engine 15 to the
auger 23 becomes excessive will be described, on the basis of FIG.
15 through FIG. 22.
FIG. 15 shows the overload prevention device 60 when the auger 23
shown in FIG. 1 is in its normal rotating state. That is, the worm
wheel 38 rotates as shown by the arrow H1; the slide washer 45 also
rotates, in synchrony with the worm wheel 38, as shown by the arrow
S1; and the auger shaft 22 and the boss member 41 also rotate in
synchrony with the worm wheel 38, as shown by the arrow B1. This is
the state before the overload prevention device 60 operates. The
stopping member 59, shown with a white circle, is not yet in
contact with the slide washer 45, and the washer detector switch
53, shown with a white square, is in its OFF state.
In FIG. 16, as a result of the auger 23 shown in FIG. 14 mounting
snow 121 or the like, the auger shaft 22 and the boss member 41
stop rotating, and the worm wheel 38 starts to slip with respect to
the boss member 41.
That is, the worm wheel 38 rotates as shown by the arrow H2, and
the slide washer 45 also rotates, in synchrony with the worm wheel
38, as shown by the arrow S2. Because the engine 15 continues to
rotate, the power from the engine 15 is transmitted through the
drive shaft 16 (see FIG. 1) and the input shaft 36 of the auger
transmission 18 (see FIG. 2) to the worm wheel 38, and consequently
the worm wheel 38 starts to rotate (slip) relative to the boss
member 41, which is in a locked state.
As shown in FIG. 17, the worm wheel 38 rotates as shown by the
arrow H3, and the slide washer 45 also rotates in synchrony with
the worm wheel 38 as shown by the arrow S3, as a result of which
the internal projections 92 of the slide washer 45 hit the external
projections 85 of the boss member 41 and the slide washer 45
stops.
As shown in FIG. 18, by the worm wheel 38 rotating as shown by the
arrow H4, the wheel protrusions 83 of the worm wheel 38 mount or
engage the disc protuberances 93 of the slide washer 45.
Consequently, the slide washer 45 moves in the obverse direction of
the figure and pushes the stopping member 59 and brings the washer
detector switch 53 to the ON state.
FIG. 18 shows the slide washer 45 in a stopped state and the
stopping member 59, shown as a black circle, in a withdrawn state,
and shows the washer detector switch 53, shown as a black square,
in its ON state.
In FIG. 19, as a result of the worm wheel 38 rotating as shown by
the arrow H5, the wheel protrusions 83 of the worm wheel 38 mount
the disc protuberances 93 of the slide washer 45. When within a
predetermined period from the first mounting this mounting is
repeated, the engine 15 (see FIG. 1) is stopped. During this time,
the slide washer 45 moves in the obverse direction of the figure
and the moves in the reverse direction of the figure the same
number of times as the number of mountings.
Because the wheel protrusions 83 of the worm wheel 38 are not atop
the disc protuberances 93 of the slide washer 45, FIG. 19 shows the
stopping member 59, shown as a white circle, not yet in contact
with the slide washer 45, and shows the washer detector switch 53,
shown as a white square, in its OFF state.
That is, in FIG. 20, the worm wheel 38 is stopped. The worm wheel
38 is shown stopped, the stopping member 59, shown with a black
circle, is in its withdrawn state, and the washer detector switch
53, shown with a black square, is in its ON state.
In FIG. 21, after the snow or other obstruction on the auger 23 is
removed, by the engine 15 being restarted (see FIG. 1), the worm
wheel 38 is rotated as shown by the arrow H5, and the slide washer
45 also rotates, in synchrony with the worm wheel 38, as shown by
the arrow S5, and the boss member 41 also rotates, in synchrony
with the worm wheel 38, as shown by the arrow B5.
In FIG. 22, as a result of the worm wheel 38, the slide washer 45
and the boss member 41 rotating in synchrony, the stopping member
59 fits in an escape hole 97 of the slide washer 45. Then, the
stopping member 59 engages with a stopping part 96 of the slide
washer 45 and stops the slide washer 45. The worm wheel 38 rotates
as shown by the arrow H6. The boss member 41 continues to rotate in
synchrony with the worm wheel 38 as shown by the arrow B6.
As a result of the worm wheel 38 and the boss member 41 rotating,
the wheel protrusions 83 of the worm wheel 38 come off or disengage
the disc protuberances 93 of the slide washer 45, and the slide
washer 45 returns in the reverse direction of the figure under the
elastic reaction of the elastic member 46 (see FIG. 2) and returns
to the initial state shown in FIG. 15.
Obviously, various minor changes and modifications of the present
invention are possible in the light of the above teaching. It is
therefore to be understood that without departing from the scope of
the appended claims the invention may be practiced otherwise than
as specifically described.
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